WASHINGTON — Rep. Susan Brooks, who disagreed with the Trump administration's decision to separate migrant parents from children, said Wednesday that a visit to the border gave her a better understanding of why it's taking time for the administration to re-unite families.

"It's very important we get this right so we are not releasing children to traffickers or other smugglers," the Carmel Republican said. "They're going to have to keep a significant amount of manpower on this effort."

Brooks was among a group of House members who visited federal immigration facilities in Texas Monday, the day before the administration fell short of a court-ordered reunification deadline.

All children under age 5 were to be reunited by Tuesday, a group that includes about 100 children. All other minors – almost 3,000 of them – must be reunited by July 26.

The children were separated from their parents under the zero-tolerance policy implemented by the administration in early May to crack down on parents crossing the border illegally accompanied by their children, many of them seeking asylum in the U.S. after fleeing poverty, violence and political turmoil in Central America.

"I wish they hadn't done the separation. And I've been clear about that from the beginning," Brooks said.

She has also signed congressional letters to the administration asking for more information about how they're handling the issue, and has said the families need to be reunited as quickly as possible.

Asked Wednesday if that's what's happening, Brooks said it is — and now she better understands some of the challenges.

One step that takes time, she said, is DNA testing of adults who claim children.

Three people claiming to be parents admitted they were not the parents when officials began to swab them for DNA testing, a U.S. Department of Health and Human Services official told reporters Tuesday.

DNA testing showed an additional three people were not the biological parents of the child they claimed was theirs.

But the only area where U.S. District Judge Dana Sabraw provided some wiggle room for the administration on timing is in cases where the parent has been deported. He said those families must be reunited under his order, but he acknowledged that those reunifications will take time.

Brooks said some parents are willingly leaving their children behind when they're deported because they might have other family members in the United States and "some parents are realizing their children are better off in our country without them."

Earlier this week, I joined a #bipartisan group of @HouseCommerce members to visit the US-Mexico border & tour facilities where children & adults are detained in order to get a 1st-hand look/better understanding of our country’s immigration process & family reunification efforts pic.twitter.com/0iqdCS6eLP

Congress has struggled to pass legislation to deal with a variety of immigration issues, including the issue of adults crossing the border with children, funding President Trump's desired border wall, and protecting undocumented immigrants that came to the U.S. as children.

Last month, the House soundly defeated an immigration bill that Republican leaders had hoped would unite warring factions within their party.

Brooks, along with Reps. Jackie Walorski and Larry Bucshon, were the only Indiana Republicans who voted for the bill.

Democrats, who united in opposition to the GOP bill, had hopes of winning support from some Republicans like Brooks for a parliamentary move to force a vote on a bill they preferred.

Brooks said she didn't join that effort because she doubted it would result in legislation that could pass the Senate and be signed into law by Trump.

Saying she was overwhelmed by the sheer number of children she saw Monday who had crossed the border — most without an adult — Brooks said the larger question is what can be done to address what's happening in their home countries that is making them flee.

"We cannot continue to have tens of thousands of unaccompanied children coming into the country," she said. "It's a massive, horrible problem."

Contributing: Daniel Gonzalez, USA TODAY Network.

Contact Maureen Groppe at mgroppe@gannett.com. Follow her on Twitter: @mgroppe.